Reject brine, generated as a waste at the end of the desalination process, presents a useful source for the extraction of valuable resources. This study investigated the recovery of reactive MgO from reject brine obtained from a local desalination plant. This was enabled via the reaction of Mg2+ present within reject brine with an alkali source (NaOH), which led to the precipitation of Mg(OH)2, along with a small amount of CaCO3. The determination of the optimum NaOH/Mg2+ ratio led to the production of the highest amount of yield. The synthesized Mg(OH)2 was further calcined under a range of temperatures (500-700°C) and durations (2-12 hours) to produce reactive MgO. A detailed characterization of MgO obtained under these conditions was presented in terms of its reactivity, specific surface area (SSA), composition and microstructure. While an increase in the calcination temperature and duration decreased the reactivity and SSA of MgO, samples calcined at 500°C for 2 hours revealed the highest reactivity, which was reflected by their SSA of 51.4 m2/g.

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In addition to its use in various applications such as those in the agriculture, pharmaceutical and refractory industries, MgO is being investigated as a cement binder due to the low calcination temperatures used during its production and its ability to gain strength by absorbing CO2 in construction products. Similar to the dry-route, the reactivity of MgO synthesised from waste water or reject brine via the calcination of the precipitated Mg(OH)2 depends on the calcination conditions. This study investigated the influence of two bases, namely ammonia solution (NH4OH) and sodium hydroxide (NaOH), on the properties of Mg(OH)2 precipitated and consequently the characteristics of MgO produced under different calcination conditions. The energy consumption of the production of reactive MgO from reject brine via the addition of NH4OH and NaOH was also reported and compared with the industrial production routes to assess the sustainability of the production procedure. The final products were characterised in terms of their specific surface area (SSA) and microstructure. Results indicated that Mg(OH)2 synthesised via the addition of NH4OH into reject brine generated a more porous, flakelike morphology than those obtained via the use of NaOH. The SSA and reactivity of NH4OH-based MgO demonstrated a sharper decrease with increasing temperature and duration compared to NaOH-based MgO. Out of all samples, NH4OH-based MgO calcined at 500 °C for 2 hours revealed the highest reactivity (SSA of 78.8 m 2 /g), which was higher than NaOH-based MgO (SSA of 51.4 m 2 /g).

Self-assembling quantum dots (QDs) have been obtained via the attachment of an outer corona of aromatic liquid crystalline (LC) dendrons to the surface of an inner alkylthiol corona encapsulating CdS nanoparticles. The dendronized CdS QDs form a cubic LC structure with an unusually low P2 1 3 symmetry. The anisotropic distribution of dendrons in the QD organic corona and in the P2 1 3 LC superlattice is thought to facilitate stacking interactions between the aromatic moieties. Moreover, the dendronized CdS QDs show LC structure-dependent photoluminescence quenching.

Recently, the mineral carbonation via the reaction of CO 2 with saline aquafers received much attention as one of the most promising ways for geologic CO 2 storage. This paper reports microstructure and carbon storage capacity of hydrated magnesium carbonates (HMCs) synthesized from different sources, i.e., reject brine and commercial Mg(OH) 2 slurry, and under different conditions, i.e., pH (8-14) and Mg(OH) 2 :CO 2 molar ratio (1:1-1:7). Results show that dypingite (Mg 5 (CO 3) 4 (OH) 2 •5H 2 O) is the main phase forming at lower Mg(OH) 2 :CO 2 ratios. An increase in the Mg(OH) 2 :CO 2 ratio and/or pH leads to the precipitation of nesquehonite (MgCO 3 •3H 2 O). A unique "house of cards" texture, involving formation of the rosette-like dypingite flakes on the surface of nesquehonite needles, is discovered under elevated pH and Mg(OH) 2 :CO 2 ratios. HMCs synthesized from reject brine exhibit a much higher carbon storage capacity of 82.6% than that produced from the commercial Mg(OH) 2 slurry (43.7%).